There is one core unit for the CLDRC, the Administrative Core Unit. The PI and co-Is in the Administrative Core Unit are all housed at the Institute for Behavioral Genetics, University of Colorado, Boulder. In pur experience with the Center, we have found that this centralized infrastructure is the most effective way to manage a project of this scale. However, this does not imply that other Center investigators are uninvolved. On the contrary, the Administrative Core Unit works under the overall supervision of the CLDRC Executive Committee, which includes all Center Principal Investigators and Co-Investigators (Figure 1). The overarching purpose of the Administrative Core Unit is to provide the infrastructure to facilitate the completion of all facets of the study. More specifically, the Administrative Core is responsible for coordinating the activities of Research Projects I-V; maintaining communication among the participating investigators; ascertaining, scheduling and paying subjects; obtaining questionnaire data from families of twins; obtaining blood or buccal samples from twins and their families and forwarding these samples to UNMC for genetic analyses by Research Project IV; preparing subcontracts and consortium agreements; managing the Center budget; and administering Center expenditures and other fiscal matters. If the present application for competitive renewal of the Center is funded, all twins and siblings ascertained by Core Unit staff during budget periods 16-20 will be administered test batteries by personnel in Research Projects Mil, and a subset of these participants will take part in the intervention study described in Research Project V. Core Unit staff will also coordinate the collection of blood or buccal samples from twin pairs and their parents and siblings, and send these samples to Research Project IV for genotyping. In addition, the Core Unit consolidates data, provides statistical support, and coordinates formal training for all projects.